Dielectric and piezoelectric properties of reduced-graphite- oxide/poly(vinylidene fluoride) nanocomposite and its related devices

Zhang, Ye (2019). Dielectric and piezoelectric properties of reduced-graphite- oxide/poly(vinylidene fluoride) nanocomposite and its related devices. University of Birmingham. Ph.D.

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Abstract

We studied the role of rGO on the dielectric properties of the nanocomposites. With a conductor-insulator heterostructure model, we found an ‘expanding’ effect of rGO particles that improves the system dielectric response. We also found a pseudo-leakage in nanocomposites due to charge carrier recombination. These findings established a quantitative method to evaluate the energy storage performance for capacitors with composite dielectrics, which fits well with the experimental data.

We also studied the molecular and crystal structure of the PVDF polymer with respect to the rGO addition. It was found that the addition of rGO can induce the nucleating of a thermodynamically instable β phase, which makes the nanocomposites ferroelectric. This β phase formation was found to occur in the melting-recrystallization procedure accompanied by the thermal reduction of rGO. A β phase formation mechanism was proposed, which suggests the nanocomposites is piezoelectric with PVDF molecular dipole mirrored by the rGO plane forming local bimorph structure. Accordingly, two types of piezoelectric devices with the rGO/PVDF nanocomposites were fabricated and tested, and the results are in good agreement with the models proposed in this research.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):